How can I set the default gateway in Windows 10 Mobile?

Windows 10 Mobile has decided not to use my WiFi network's default gateway any more. Other devices work in the network and the Windows 10 Mobile device works with other networks.

I tested and saw that it does connect to the network and can connect to local Web sites (in my house). It also receives DNS servers or so the settings tell me, just no default gateway (192.168.1.1 in this network).

How can I force a default gateway on Windows 10 Mobile when it refuses to use the one DHCP tells it to use? Everything I find on Google assumes regular Windows 10 and suggests ways that are blocked on Windows 10 Mobile.